DESCRIPTION (taken in part from the application's abstract) This project is specifically intended to clone the defective genes that are responsible for the inability to absorb iron in two inbred strains of mice, called microcytic (mk) and sex-linked anemia (sla). The project involves the development and characterization of cell lines derived from intestinal cells of the mk and sla mice and erythroid cells of the mk mouse. Iron metabolism in these cell lines will be characterized by examining the expression of genes known to be responsive to intracellular iron concentration (ferritin and the transferrin receptor) and reporter constructs whose expression depends upon the well-characterized iron regulatory element binding protein. The approach to cloning the defective mk and sla genes is one of functional complementation of the abnormal phenotype using cDNA library transfection and selection of cells complemented with the normal gene by use of iron-dependent expression of antibiotic resistance genes. The isolation and characterization of these genes should provide clues to how mammalian cells regulate iron transport and uptake, and might result in the development of new candidate loci for a number of human disorders of iron metabolism.